The present subject matter relates generally to systems and methods for securing write and erase operations in a memory device. More specifically, the present subject matter provides systems and methods in which a filter logic device is employed between a memory device and the system in which it is used to filter commands from the system to the memory device.
There are many computer systems in which one or more memory devices are used to store critical information within the computer system. While there are nearly limitless variations of such systems and environments in which they are used, the disclosure provided herein discussed the subject matter in the context of gambling machines. While described in the gambling machine context, it is understood that the teachings provided herein are applicable to any system in which one or more memory devices are used within the computer system.
Computer systems for use in gaming and gambling machines are often referred to as “slot machines.” It is usually necessary for slot machines to comply with certain standards defined by government, state, or other regulatory bodies relating to the security of the slot machines, as they handle significant revenue streams. It is usual for there to be security requirements to ensure the machines are not tampered with, for example, to prevent manipulation of payouts to users or prevent tampering with the recording of transactions for the purpose of collecting government gaming taxes from machine operators. Of course, in other contexts, there may be additional or alternative regulatory security requirements.
Slot machine manufacturers also have a strong interest in security in order to protect their intellectual property and prevent cloning of their systems or designs and/or the use of legitimate machines outside of the agreed terms, for example installation of a newer game on a machine without payment. Again, in other contexts, there may be additional or alternative commercial security requirements.
As part of these security requirements (whether commercial or regulatory), it is usually necessary or valuable to be able to be able to protect certain memory devices from having their content modified (modified, overwritten, or erased) with a physical write-protection in order to prevent any attempt at tampering or unauthorized change. In slot machines, it is often a requirement that a physical jumper or switch is included should it be necessary to provide physical write-protection. The physical switch or jumper can be protected by a seal or other physical protection mechanisms that prevent unauthorized access and/or leave a telltale physical sign if someone has tampered with the physical write-protection.
While some memory devices include an electrical write-protect signal that, when asserted, prevents any write or erase of the memory device. However, many memory devices do not include intrinsic methods for electrical control over write or erase operations. These memory devices have been unusable when such security requirements exist. As a result, when there are security requirements, the choice of memory device is restricted by what is available in the market that works with the system. If a suitable device with intrinsic electrical write-protection is not available, there can be significant issues.
Accordingly, there is a need for systems and methods to provide electrical control of write and erase operations in memory devices that otherwise lack such security features.